As described in my U.S. Pat. No. 3,608,734, a highly successful form of liquid filtering apparatus is comprised of a plurality of horizontal plates which are arranged in a vertical stack. The plates are shaped with side walls and transverse portions that form enclosed cavities or chambers when they are pressed together. With a sheet of filter media located between each pair of adjacent plates, a chamber for incoming unfiltered liquid is formed on the upper side of the sheet, with a cavity for the filtered liquid below the sheet. When necessary, the plates are separated by being moved upwardly to allow fresh sheets of filter media to be positioned between plates, and when thus positioned, the plates are brought together by a vertically directed force sufficient to seal the peripheries of the plates and thus form the aforesaid liquid-tight chambers and for dirty and clean liquid on opposite sides of each filter media sheet. In order to adequately seal the plates as they are closed at the end of each media changing cycle, the vertical force exerted must not only be sufficient, but it is also essential that adjacent plates of an entire stack be maintained in perfect alignment relative to each other so that their sealing elements function properly. Maintaining such proper alignment has heretofore been a problem because often the plates become misaligned as they are lifted and separated. Consequently, when the plates were again pressed together after the filter media was changed, it was often difficult to achieve an adequate seal without using excessive closing force on the plates because there was no assurance that each plate would align itself exactly in the same position for proper sealing each time.
The requirement for a relatively large vertical closing force created a related problem in that, under certain circumstances, it caused excessive loads to be exerted on structural elements of the plates, such as their side walls. This became particularly critical when the plates were constructed from a plastic material instead of a stronger metal for filters which must be capable of handling corrosive liquids.
It is, therefore, one object of the present invention to overcome the aforesaid problems by providing a means for maintaining the proper alignment of a plurality of plates in a horizontal plate type filter as the plates are repeatedly separated and then closed to facilitate the advancement of filter media between pairs of adjacent plates.
Another object of the present invention is to provide an improved plate for a horizontal plate type filter that enables it to be more readily aligned and sealed with adjacent plates when the plates are pushed together.
Yet another object of the invention is to provide for the alignment of vertically separable and closeable plates in horizontal plate filter that also includes stop means for limiting the contact pressure between adjacent plates and thus, the stress on the plate as the side walls are closed together.
Another object of the invention is to provide an improved filter plate for horizontal plate-type filtering device that may be fabricated from nonmetallic, noncorrosive plastic materials.
A further object of the present invention is to provide an improved filter plate with alignment and stop means which is particularly well adapted for ease and economy of manufacture.